The present invention relates to a plasma processing apparatus or a plasma processing method that processes a substrate-shaped sample such as a semiconductor wafer in a processing chamber in a vacuum container using plasma formed therein.
A plasma processing apparatus processes a sample such as a semiconductor wafer mounted on a sample stage using plasma generated above the sample and removes a target film from the surface of the sample through chemical reaction between the plasma and the sample or causes a film to be deposited onto the surface of the sample. The former is called “etching processing” and the latter is called “CVD (chemical vapor deposition).”
In such plasma processing, processing proceeds through chemical reaction between ions or active gas species and the sample using chemically active plasma. Whether a chemical reaction occurs or not, or whether a byproduct generated by a chemical reaction becomes a gas and is desorbed/released (etched) from the surface of the sample or a byproduct is solidified and deposited onto the surface of the sample (CVD) is greatly influenced by a temperature of the sample.
For example, when a sample of a material whose byproduct has a low vapor pressure is etched, it is necessary to reduce a pressure in a plasma processing chamber or increase a sample temperature so that the byproduct becomes a gas and is desorbed/released from the surface of the sample. Stably maintaining a plasma atmosphere requires the plasma processing chamber to actually have a certain degree of pressure (≧ on the order of 0.1 Pa) and also requires the sample temperature to be sufficiently high.
In this way, it is necessary to control the sample temperature in accordance with a target process. Thus, a method is adopted which controls the sample temperature to a desired temperature by controlling the sample stage temperature. As such a configuration of adjusting the sample stage temperature, conventionally, a temperature-controlled heat exchange liquid is made to flow through the sample stage or a heater is incorporated in the sample stage for heating.
On the other hand, the sample temperature is adjusted through a heat transfer to/from the sample stage. For an efficient heat transfer between the sample and a top surface of the sample stage on which the sample is mounted, it is a general practice that the sample is chucked to the mounting surface by an electrostatic chuck force or the like and a heat transfer gas such as a He gas is supplied to a clearance space between the sample and the mounting surface. Furthermore, since such temperature adjustment of the sample is greatly influenced by heat transfer efficiency, electrostatic chuck conditions for holding the sample onto the mounting surface and a region to be chucked to improve a heat transfer have been conventionally taken into consideration.
As such a prior art, one described in JP-A-09-167794 is known. This prior art discloses a technique which supplies a heat transfer gas to a wafer held on a sample stage by a plurality of dipolar chuck electrodes to adjust a wafer temperature, then keeps the wafer chucked onto the sample stage while causing the plurality of chuck electrodes to operate as monopolar electrodes, and thereby processes the wafer.